At issue is a 1975 California law that allows union organizers limited access to farms so they can seek support from workers in forming a union.

Transcript

STEVE INSKEEP, HOST:

Today the Supreme Court hears arguments in a case that pits the rights of farmworkers and labor unions against large agricultural employers. At issue is a law passed in California back in 1975 and still in effect today. It's a law that stemmed from the work of the famed union organizer Cesar Chavez. It allows union organizers limited access to farms so they can seek support from workers in forming a union. Here's NPR legal affairs correspondent Nina Totenberg.

NINA TOTENBERG, BYLINE: The growers challenging the law contend that by giving union organizers a limited right of access to farms, California is authorizing a mass trespass on their private property, and that, they argue, amounts to an unconstitutional taking of their land, requiring the government to pay them just compensation. The case before the court began in 2015 at the Cedar Point Nursery near the Oregon border.

UNIDENTIFIED PERSON: (Non-English language spoken).

(SOUNDBITE OF ARCHIVED RECORDING)

MIKE FAHNER: You may as well call it an ambush. And we had no idea, no forewarning, that there was any desire, need, for the UFW's presence or a strike, for that matter.

TOTENBERG: Strawberry grower Mike Fahner says in a widely distributed video that union organizers, without giving the required notice, showed up with bullhorns harassing his workers.

(SOUNDBITE OF ARCHIVED RECORDING)

FAHNER: If this were to happen in any other industry, in any other state, the people would be expecting to be arrested and taken away in handcuffs.

TOTENBERG: United Farm Workers general counsel Mario Martinez says that account is a lie.

MARIO MARTINEZ: It's absolutely false. All the people that you see on the video that has been circulated by this grower are workers employed by Cedar Point going out on strike.

TOTENBERG: In other words, he says, the people seen demonstrating are not UFW union organizers but workers on strike. For the union, the case is an existential threat. Farmworkers in California are seasonal. Typically working for several employers during the course of the year, they arrive in town in time for the local harvests, live in motels, labor camps or with friends or relatives, then move on when the crop is picked. In practice, that means organizers can gather signatures for a union election only during the relatively short harvest time at a particular site.

Because of these and other farm-specific conditions, under California's labor regulations, union organizers are permitted to meet with workers an hour before and after work and at lunchtime, all on the growers' property, for limited periods during the year. Cedar Point Nursery owner Fahner contends that California's agricultural labor law is a relic of the past.

(SOUNDBITE OF ARCHIVED RECORDING)

FAHNER: This law in today's world is no longer necessary. With social media - Facebook, Snapchat, WhatsApp - you can communicate with people around the world effectively, without having to have access to a person's private property and place of business.

TOTENBERG: The union's Martinez calls that argument nonsense, noting that most of the migrant workers are undocumented Indigenous people who don't speak English, have little education and don't have modern smartphones with access to the Internet or Wi-Fi.

MARTINEZ: And importantly, most of these workers do not know of the existence of their right to organize and form a union. So in the UFW's experience, it's critically important to have face-to-face communication with these workers.

TOTENBERG: This is not the first time California's labor law has reached the Supreme Court. In 1976, the California Supreme Court ruled against a similar challenge brought by the growers, and the U.S. Supreme Court declined to take up the case. But now, with a far more conservative high court in place, the growers are trying again, and it's significant that the justices agreed this time to hear the case.

If the newly energized conservative Supreme Court majority agrees with the growers this time, the decision could have profound consequences for other laws, laws allowing health and safety inspectors at every level of government to enter businesses to examine how meat is butchered, whether mines are safe, how toxic chemicals are stored, whether nursing homes are taking proper care of their patients, whether businesses are in compliance with fire and building codes and on and on. So a decision in favor of the growers arguably could undermine many other laws aimed at protecting not just migrant workers but the American public. Nina Totenberg, NPR News, Washington. Transcript provided by NPR, Copyright NPR.